Plasmalogens are a class of phospholipids characterized by the presence of a vinyl-ether-linked alkyl chain at the sn-1 position, an ester-linked long-chain fatty acid at the sn-2 position, and a head group attached to the sn-3 position through a phosphodiester linkage. They are represented by the following general formula:

In mammals, the sn-1 position is typically derived from C16:0, C18:0, or C18:1 fatty alcohols while the sn-2 position is most commonly occupied by polyunsaturated fatty acids (PUFAs). The head group can have different identities such as ethanolamine, choline etc.
Plasmalogens are found in numerous human tissues, particularly, in the nervous system, the immune system and the cardiovascular system. They represent one fifth of the total phospholipids in the human body. Plasmalogens are thought to have numerous physiological roles: they are an important structural component of the cell membranes, and act as secondary messengers in cell signaling. In fact, almost 30% of the glycerophospholipids in the adult human brain and up to 70% of myelin sheath ethanolamine glycerophospholipids are plasmalogens. They may also be involved in membrane fusion, ion transport, and cholesterol efflux. Plasmalogens may also act as antioxidants, thus protecting cells from oxidative stress (Plasmalogens: Workhorse Lipids of Membranes in Normal and Injured Neurons and Glia. Akhlaq A. Farooqi, Lloyd A. Horrocks; Neuroscientist. 2001 June; 7(3):232-45.).
Apart from their normal physiological roles which are still being elucidated, plasmalogens are also implicated in different human diseases (Functions and biosynthesis of plasmalogens in health and diseases, Pedro Brites, Hans R Waterham, Ronald J. A Wanders; Biochim Biophys Acta. 2004 Mar. 22; 1636(2-3):219-31.). In particular, altered levels of tissue plasmalogens has been associated with Zellweger syndrome, rhizomelic chondrodysplasia punctata, Alzheimer's disease, Down syndrome, and Niemann-Pick type C disease etc. (The ether lipid-deficient mouse: tracking down plasmalogen functions. Gorgas K, Teigler A, Komljenovic D, Just W W., Biochim Biophys Acta. 2006 December; 1763(12):1511-26).
A number of reports have been published demonstrating reduced levels of brain plasmalogens in Alzheimer's disease (Plasmalogen synthesis is regulated via alkyl-dihydroxyacetonephosphate-synthase by amyloid precursor protein processing and is affected in Alzheimer's disease, Grimm M O, Kuchenbccker J, Rothhaar T L, Grösgen S, Hundsdorfer B, Burg V K, Friess P, Müller U, Grimm H S, Riemenschneider M, Hartmann T., J Neurochem. 2011 March; 116(5):916-25; Membrane phospholipid alterations in Alzheimer's disease: deficiency of ethanolamine plasmalogens, Farooqui A A, Rapoport S I, Horrocks L A, Neurochem Res. 1997 April; 22(4):523-7.)
The administration of plasmalogens as dietary supplements is now being considered for treatment of Alzheimer's disease.
However, the mechanism of action as well as the fate of plasmalogens in the body is still not completely understood. It is therefore of interest to study the metabolism of plasmalogens in the body. Also, if plasmalogens are to be administered as a dietary supplement, the fate of the plasmalogen supplement administered needs to be known.
Thus stable metabolic tracers for plasmalogens are needed.
Chemical synthesis of plasmalogens can be used to synthesize 13C labeled plasmalogens which can be used as metabolic tracers. Several approaches have been tried to chemically synthesize plasmalogens (Direct Synthesis of Plasmenylcholine from Allyl-Substituted Glycerols, Junhwa Shin and David H. Thompson, J. Org. Chem., 2003, 68 (17), pp 6760-6766; Improved to Plasmalogen Synthesis Using Organobarium Intermediates, Jeroen Van den Bossche, Junhwa Shin, s and David H. Thompson, J. Org. Chem., 2007, 72 (13), pp 5005-5007). However, most of the existing chemical synthesis processes face problems due to sensitivity of the vinyl-ether bond to acidic conditions as well as oxidative conditions. Further, there is also a difficulty in generating the Z—O-alkenyl functionality stereoselectively.